Reactions to heavy metal salts

The salts of heavy metals occupy a special position among the pollutants
of the ecosystem. It is
known that not only the different species of plants, but also
separate types and even clones are distinguished by their sensitivity to
the specific contaminant. Special bioassays for determining the effectiveness
of the general/common action of pollutants are reduced to the estimation/evaluation
of the degree of a change in readily measured morphometric and biochemical
indices, the estimation/evaluation of germination vigor, energy of an root
growth, vulnerability of plants to the effect of the contaminant. The degree
of the depression of the plants after a treatment is determined by physiological
methods.

For the purpose of our studies, we made a search for rapid and adequate
tests with which it would be possible to determine the pollution/contamination
of soil and water by salts of heavy metals, pesticides, to analyze soil
from the diverse variants of field monitoring with the complex pollution/contamination.
Different forms of duckweeds, which are encountered in the territory of
Krasnodar edge, served successful as test object.

During the first stage of our work we began to determine the reaction
of each specific contaminant (metal or pesticide), and then to conduct
complex soil testing.

Reactions to the metals.

Studies were undertaken on the aqueous solutions of the following salts:
ZnSO4, CuSO4, CuCl2, Co(NO3)2,
BaCl2, MnSO4, and Fe2(S04)3.
We show the reaction of duckweeds to the metals by means of the three tables
below. This presentation, in our view, allows us to most fully illustrate
entire spectrum of the responses to each concentration of these metals.

Two forms - ivy-leaf duckweed (Lemna trisulca)
and rootless water meal (Wolffia arrhiza)
reacted to the action of pollutants with a change in the color of the fronds
and there was little other information. For these species we, therefore,
limited themselves to a brief description, without the introduction
of a table.

Ivy-leaf duckweed is completely immersed in the water. Therefore
it more rapidly responds to pollution/contamination - either it dies off
completely or is the intensity of its pigmentation changed . Apparently
for this form it is necessary to search for other evaluation criteria,
with
the use of color and other cytological methods capable of giving complete
information
about the degree of contamination of water.

The rootless Wolffia plant is very small, without roots which
hamper analysis upon transfer from one concentration of metal to another.
This plant, nevertheless can be used successfully for phytotoxicity testing
for passive monitoring of pollution/contamination of natural reservoirs.

Concentrations 0,1- 0,25 of all the metals tested proved to be lethal
for all representatives of Lemnaceae, in this connection we combined them
in one graph (tables 1, 2, 3).

Figure 1. Lemna minor. Cu -copper - 0,001-0,0001
mg/mL (reaction five hours after experiment) Fronds are decolorized from
the edge to the center,frond disconnection is complete.

Copper (Cu) - the first reaction to the metal with the
concentrations:0,1 - 0,25 - 0,025 -appeared 4 hours after the beginning
of the experiment. Fronds were decolorized, (Fig. 1) and by the next
day they had acquired a bluish pigmentation. Wolffia fronds
at a concentration 0.001 Cu were decolorized. Green pigmentation
was preserved in ivy-leaf and lesser duckweed only at the points of increase/growth
with complete disconnection of fronds. In greater duckweed, fronds
became light green and disconnected (Fig. 2).

a)

b)

Transparent thread, whichconnects four fronds andtwo turions.

Specific reaction to copper: a) control,
all fronds of small duckweed are assembled into groups; b) versionwith copper, all fronds were disconnected and the frondsturned brown.

Cobalt (Co) In comparison with all forms of duckweeds, more sensitive
than all reacts the Lemna minor (table 1, 2, 3). It is noted:the
loss of painting/color, fronds they get dry from the edges and are separated.Apparently,
the way this of entering it threw it passes along the vascular beams is
caused lightening the cloths of fronds along the veins (fig 4, 5).